Three-Phase Induction Motor Construction: Interactive 3D Model

Drag the model to turn it. Use the slider to explode the motor into its parts. Switch between the squirrel cage and phase-wound (slip-ring) rotor. Click any part to read what it does. Turn on Reveal internal structure to make the internal parts easier to see.

Three-phase induction motor: 3D construction viewer

Rotor type

Explode

Cut-away frame Animate rotor Reveal internal structure

Phase R Phase Y Phase B Field N Field S

Parts

Click a part in this list or on the model.

What this model shows, and what it simplifies

Valid for three-phase induction motors only. A single-phase motor has a different stator winding and needs a starting arrangement.
The motor is a 4-pole, 50 Hz machine. Synchronous speed N_s = 120f / P = 120 × 50 / 4 = 1500 rpm.
Stator: 36 slots, which is 3 slots per pole per phase. Cage rotor: 28 skewed slots. Wound rotor: 24 slots. The rotor slot count is never equal to the stator slot count.
Windings are drawn single-layer and full-pitch, one coil side per slot, so you can follow each phase. Many real motors use double-layer, short-pitch windings.
The air gap, shaft and end shields are drawn larger than true scale so that every part is visible. Proportions are illustrative, not from a datasheet.
In the animation the rotor is shown running slightly slower than the rotating field. A real motor at full load typically has about 2–5 % slip.

Read more:

Common mistakes this model helps you avoid

Thinking the rotor is connected to the supply. In both rotor types, current is induced in the rotor. Only the stator is supplied.
Thinking the rotor can reach synchronous speed. At s = 0 there is no relative motion, no induced emf and no torque.
Adding external resistance to a cage rotor. Its bars are permanently short-circuited by the end rings. Only the slip-ring rotor has an accessible rotor circuit.
Forgetting that the stator and rotor cores are laminated, not solid. Solid iron would give large eddy-current losses.

Also Read: Squirrel cage rotor types and Production of rotating magnetic field.

FAQ

Why are the rotor slots skewed?: Skewing reduces magnetic locking between rotor and stator teeth and makes the motor run more quietly.
Why does the wound rotor have slip rings?: They bring the three rotor winding ends out to brushes, so an external rheostat can be connected to adjust starting torque and speed.
Is the 3D model accurate to a real motor?: The parts, their arrangement and their functions are accurate. Dimensions, slot shapes and winding layout are simplified for clarity.